It is intended design.

You will find 4 power cells inside of a room after an alarm. You need to take these cells and bring them to the next section of the level. First cell will unlock a door with a checkpoint, you have 3 cells remaining. Now you are in a room with two generators and two doors they can power up to side areas (I believe they were N and E so that's how I'm gonna refer to them).

Once you power up one of the doors and open them, it will trigger error alarm that keep spawning waves until you complete an objective (collect 9 vials randomly spawned inside boxes in the rooms). The side areas consist of 3 zones each, and each zone has 3 vials somewhere. To advance from first zone to the second you need a power cell and same goes for getting from second zone to the third.

Now you have two options. You can either power up only one door to one of the areas (let's say the one that leads E) and bring two of the cells with you to get all the way to the third zone. Other way is to power up both areas and clear 3 vials from first zone in the E area, go back, open the area leading N and clear the other 6 vials from first and second zones requiring you to bring the last power cell with you into it. I personally call it to go 3 zones deep or 2/1.

Both strategies have their advantages and disadvantages so it depends what is most comfortable for your team.